Windshield wiper systems used on most automotive vehicles have a whiffle-tree wiper superstructure for carrying the wiper blade. Such a system has many metal linkages, a single or double vertebrae, and many riveted joints with tight clearances. A typical system also includes claws for attachment of a rubber wiping blade. While such a structure works well in many circumstances, there are various drawbacks which make an improved wiper assembly desirable. One drawback is that moisture may seep into the riveted joints and freeze in colder temperatures preventing the wiper from flexing and thus causing it to separate from the windshield. Another potential drawback of the whiffle-tree wiper system is a large pressure variation along the length of the wiper blade causing smearing and streaking during wiping operations. This pressure variation is typically caused when the claws are spaced too far apart so that a high pressure area develops under each claw and low pressure areas develop between claws. This non-uniformity in wiper pressure may cause localize wiper blade element deformation which, over the course of time, may lead to a permanent set in the wiper element. Such a permanent set would invariably require wiper element replacement.
Another disadvantage of conventional wiping systems is an inability to uniformly wipe high curved portions of the windshield which are typically at the laterally outermost edges thereof. The wiper may not be in contact with the windshield at the outer extremes, thus allowing snow, ice and other debris to build up.
As a further complication, windshield curvature varies, in some cases substantially, across vehicle models thus requiring specialized wiper system designs for each vehicle model. One attempt for providing a wiper system to address some of the aforementioned problems is shown in U.S. Pat. No. 4,976,001 (Wright). The design in Wright forms a carrier by two similar parts, each being the mirror image of the other part to form a longitudinal recess for the wiper blade as well as a spline. Transverse grooves in the spline form confronting and abutting surfaces that promote flexibility of the spline. The disclosed design in Wright requires several parts to be assembled and, disadvantageously, has the transverse grooves along nearly the entire length of the wiper system, including the center of the windshield where a uniform wipe is important. Further, the Wright system is susceptible to precipitation freezing between the transverse grooves in the center area leading to non-uniform wiping.
There is thus needed a windshield wiping system which provides flexibility to accommodate high curvature portions of a windshield, which provides a uniform wipe pressure distribution over the central portion of the windshield, which has few parts to be assembled and which is not susceptible to wipe degradation under frozen precipitation conditions.